| 摘要: |
| 【目的】明确放牧强度对生物土壤结皮（生物结皮）分布格局的影响。【方法】以黄土丘陵沟壑区4个典型的退耕还林（草）县（市）的退耕草地为对象，以单位面积羊粪球数(羊粪球密度)表征放牧强度，将放牧强度划分为轻度（羊粪球数0~10个/m2）、中度（羊粪球数＞10~20个/m2）、重度（羊粪球数＞20个/m2）3个强度，分别记作G1、G2、G3，以退耕封禁草地为对照(G0)，基于景观生态学方法，通过拍照和GIS图像处理，采用景观格局指数定量分析了生物结皮分布格局的变化。【结果】放牧影响退耕草地生物结皮的盖度及组成，其中G2和G3处理藓结皮盖度显著低于G0和G1处理；藻结皮盖度随放牧强度的增加呈增大趋势，地衣结皮盖度无显著变化。放牧降低了生物结皮厚度，其中G3处理生物结皮厚度显著低于G0和G1处理。随着放牧强度的增加，藻生物量呈增大趋势，但各处理间差异不显著；而藓生物量呈降低趋势。与G0处理相比，放牧显著降低了生物结皮斑块的连结度，而增加了分离度，其中G3处理斑块连结度显著降低，而分离度显著增加。随着放牧强度的增加，生物结皮斑块密度变化不显著，斑块盖度、斑块连结度降低，而景观形状指数、分离度增加。放牧强度与生物结皮斑块盖度、斑块连结度、斑块分离度之间显著相关，拟合结果显示均呈二次函数关系。【结论】中度和重度放牧强度（羊粪球数>10个/m2）导致生物结皮斑块破碎化及退化。 |
| 关键词: 黄土丘陵沟壑区 生物土壤结皮 放牧强度 斑块格局指数 斑块连结度 斑块分离度 |
| DOI： |
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| 基金项目:“西部之光”交叉团队 重点实验室合作研究专项（2019年资助）；国家自然科学基金重点项目“黄土高原生物结皮对坡面水土流失过程的影响及模拟”（41830758） |
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| Effects of grazing intensity on distribution pattern of biological soil crusts in loess hilly and gully region of the Loess Plateau in China |
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QIAO Yu,ZHAO Yunge,MA Xinxin,et al
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| Abstract: |
| 【Objective】The research aimed to clarify the influence of grazing intensity on distribution pattern of biological soil crusts (biocrusts).【Method】Four representative abandoned grasslands with different grazing intensities (represented by number of goat dung pellets per square meter) in loess hilly and gully region were selected and the grazing intensities were divided into light grazing (G1),moderate grazing (G2) and heavy grazing (G3) according to the numbers of goat dung pellets of 0-10,>10-20 and >20 m-2,respectively.The enclosed rehabilitated grasslands were used as the control (G0).Based on the method of landscape ecology,the distribution patterns of biocrusts under different grazing intensities were quantitatively analyzed by landscape pattern index through photography and GIS image processing.【Result】Grazing affected the coverage and composition of biocrusts,and the coverages of moss crusts in G2 and G3 treatments were significantly lower than that in G0 and G1 treatments.With the increase of grazing intensity,the cyanobacteria crust coverage increased,but lichen crust coverage had no significant changes.Grazing reduced the thickness of biocrusts,and G3 had significantly lower thickness than that G0 and G1 treatments.With the increase of grazing intensity,algae biomass increased without significant differences while moss biomass showed a decreasing trend.Grazing significantly reduced the patch cohesion index of biocrusts and increased splitting index of biocrusts.Compared with enclosed site,the patch cohesion index of biocrusts of G3 treatment was significantly lower and the splitting index of biocrusts was higher.With the increase of grazing intensity,patch density of biocrusts changed insignificantly,ratio of patch to landscape area and patch cohesion index decreased,and landscape shape index and the splitting index of biocrusts increased.Grazing intensity was significantly related to ratio of biocrusts patch to landscape area (PLAND),patch cohesion index of biocrusts (COHESION),and splitting index of biocrusts (SPLIT) with quadratic function relationships.【Conclusion】Moderate and heavy grazing intensities (goat dung pellets>10 m-2) caused patch fragmentation and biocrusts degradation. |
| Key words: loess hilly and gully region biological soil crusts grazing intensities patch pattern index patch cohesion index of biocrusts splitting index of biocrusts |
